hello and welcome to the part 1 of the two-part lesson on ADD local sizing task ansys fluent is the industry leading fluid simulation software known for its Advanced physics modeling capabilities and industry-leading accuracy before starting the simulation in ansys fluent the geometry is required to be meshed with acceptable quality preparing a high quality cfd mesh can be very time consuming and challenging task but this can be done with ease using ansys fluents watertight geometry workflow machine which greatly reduces Hands-On meshing time and enhances efficiency it has a guided workflow which makes meshing simple and intuitive in this lesson we will discuss about the import geometry task with focus on CAD import and Edge face and body sizing size control types available under the add Locus as in task of the ansys fluent water type geometry workflow machine so without further delay let's get started [Music] [Applause] [Music] thank you launch ansys fluent in meshing mode and start a new watertight geometry workflow in ansys fluent machine in the import geometry task there are two file import options available the cad import which starts from a cad geometry and the mesh import which starts either from an existing surface or volume mesh file or an ansys fluent case File here we will focus on the cad import an important requirement for using the watertight workflow is that the cad geometry must be relatively clean with watertight regions clean CAD refers to error-free geometries whereas watertight cats refer to geometries with no gaps holes or leaks the cad geometry is used in the watertight workflow can be a single body part or a combination of multiple bodies the cad import type supports any combination of fluid and or solid bodies in addition to solid and fluid volumes the watertight workflow also supports importing of geometries with voids when dealing with multi-body parts each of the bodies fluid or solid should be individually watertight it is recommended that the share topology operation is performed on geometries involving multiple bodies finally it is recommended to group surfaces and create labels before importing the geometry into ansys fluent machine these labels are useful for adding local sizes and are subsequently identified by ansys fluent when assigning boundary conditions during the simulation stage for input geometry units we have different units available here we will select mm for units as the geometry has been prepared in millimeter unit once done click import to load the cad into the workflow once the geometry is successfully imported turn on insert clipping planes in the clipping planes section of the ribbon and select limit by Z we can now see the inside of our geometry where we have three square boxes enclosed by a larger box the next task is the add local sizing local sizing refers to the set of instructions related to mesh sizing given to the meshing algorithm to apply to specific parts of the geometry or localized regions local sizing is extremely helpful at the surface mesh level to ensure all the necessary geometrical features are appropriately resolved it is also required at the volume mesh level to not only capture the fluid flow features that occur over a wide range of length scales but also to resolve strong gradients in the flow field such as in the wake of an object changing the would you like to add local sizing option to yes enables you to define the local sizing controls as mentioned earlier we will be looking at the edge face and body size controls of the add local sizing task let's now start with the face size in the add local sizing section under size control type select face size the face size control type lets the user specify the size of the mesh that is applied on the selected surfaces of the geometry this is specified in the Target mesh size input box in our case let's use 1mm note that all locals as in control types are soft sizings meaning that the target mesh size value defines the maximum mesh size for the selected surface or region it is possible for the mesh to be smaller than the target size depending on the other sizing settings let us select the body 2 faces surface notice that the boxes are overlaid onto the selected surface in the graphics window this is the dynamic preview of Target mesh size that will be imposed on the surface because of employing face size control as you change the target mesh size the sizes of boxes also change accordingly you can use the clear preview button to erase the size boxes and select the target mesh size input box to redraw them to entirely stop the dynamic preview uncheck the draw size boxes option the final option that we need to discuss here is the growth rate growth rate defines the rate at which the mesh size increases away from the selected entity this parameter becomes critical when generating the volume mesh the default value of 1.2 is sufficient for most problems however for accurately resolving certain flow phenomena like laminar turbulent transition or when performing scale resolved simulations like Les it is recommended to use a growth rate of 1.1 or less since we have defined all the necessary settings click on ADD local sizing to confirm the local sizing control let us now discuss the edge sides and body size controls as the names suggest Edge sizing refers to a local sizing control that is specified on the edges of the geometry and body sizing refers to the local sizing control that is specified on bodies or closed volumes The Edge sizing control is only visible when there are named selections that have been defined for one or more edges of the geometry other than the difference in the type of entity being picked all other options and settings are identical to the face size control however the impact each of these controls will have on the surface and final volume mesh is different note that we can Define as many local sizings as needed on different surfaces or regions with different settings and of different control types in the workflow add two more local size controls and Edge sizing for body 1 edges region and a body sizing for body 3 body region both with a Target mesh size of 1 mm foreign s are defined go to the generate surface mesh task leave all the settings to default and click generate surface mesh here is the surface mesh you should obtain body 1 shows a starkly different mesh distribution compared to body 2 and body 3. this is simply because the local sizing is specified only for the edges of this body at the surface mesh level the influence of both face and body sizing looks identical let us now go through the workflow and create a volume mesh other than changing the geometry type to the geometry consists of both fluid and solid regions and orbites in the describe geometry task you can keep the default settings and values for the rest of the tasks and execute each one of them till they generate the volume mesh task in the generate the volume mesh task select poly hex core for the fill width option and click the generate the volume mesh button here is the generated volume mesh now you can vividly see the difference between the three sizing controls the edge size and the face size controls have the mesh clustered only near the edges and the faces respectively whereas because of applying the body size control all the cells inside body 3 have been created with the same cell size we can also notice the effect of the growth rate by looking at how the locus has in propagates inside and outside the cubes by using a lower value like 1.1 in all local sizing we can see how the transition is delayed this brings us to the end of this lesson let's summarize what we have learned in this lesson we learned why meshing is required and what ansys fluent meshing water digiometry workflow is then we learned about the import geometry task and the geometry requirements of watertight geometry workflow finally we discussed about the add local sizing task and Edge face and body size control type options available inside it with that let's wrap up the lesson